Selective catalytic reduction (SCR) catalysts are subject to deterioration in performance resulting from the accumulation of various contaminants such as urea and hydrocarbons on the SCR catalyst. In exhaust systems that include, for example, active particulate filter regeneration, the particulate filter regeneration event can serve in part as a regeneration event for the SCR catalyst and other catalysts as well to remove urea deposits and to desorb hydrocarbons. However, certain aftertreatment systems do not include a particulate filter requiring periodic regeneration.
In other systems, exhaust gas temperatures are raised by controlling and opening of in inlet to a variable geometry turbine (VGT) in the exhaust system. However, VGT's are expensive and control of the opening can be complicated depending on engine operating conditions to achieve the desired result. Other systems also do not actively manage SCR catalyst contamination. As a result, the SCR catalyst may be required to operate while contaminated until operating conditions are provided that produce exhaust gas temperatures that desorb hydrocarbons and remove urea deposits. Therefore, further technological developments are desirable in this area.